1. Field of the Invention
The present invention relates to a method of switching service profiles of a remote terminal from one to another according to a given condition, and a terminal apparatus for utilizing the method.
2. Description of the Related Art
An ISDN (integrated services digital network) manages service profiles, which are information pieces including user telephone numbers and services given to users. A service is supplied to a user's terminal apparatus according to a service profile identifier (SPID) that is transmitted from the terminal apparatus to the network when a layer-2 link is established between them. The service profiles and end-point initialization are specified in ITU-T Recommendation Q.932. It should be easy to switch the service profiles from one to another, in order to expand the range of use of the service profiles.
According to a prior art, a service profile identifier (SPID) for specifying a service profile in an ISDN must directly be registered to a terminal apparatus. The terminal apparatus requests the network to initialize an end point according to the SPID. Whenever a different user uses the terminal apparatus, the user must register its own SPID to the terminal apparatus.
When the terminal apparatus requests the network to initialize the end point according to an SPID, the network allocates a service profile to the terminal apparatus and transmits information related to the service profile to the terminal apparatus. The terminal apparatus downloads the information and allocates functions to physical keys according to the downloaded information. At this time, a feature corresponding to the service profile is newly activated even if the feature has been activated previously.
A terminal apparatus of an ISDN is used in various ways. It may be used by different users. In this case, each user must enter its own SPID whenever the user uses the terminal apparatus. When the terminal apparatus is used at predetermined hours or on predetermined days by a specific user, the SPID must be entered into the terminal apparatus each time. This is troublesome.
Each SPID must be unique in the network. Namely, terminal apparatuses are not allowed to use the same SPID at the same time. If a second terminal apparatus sends an SPID, which is already registered in a first terminal apparatus, to the network, the network rejects the request to initialize an end point of the second terminal apparatus according to the SPID.
In this case, the user of the second terminal apparatus calls the user of the first terminal apparatus and asks him or her to delete the registered SPID and release a service profile for the SPID. Thereafter, the user of the second terminal apparatus the SPID to the second terminal apparatus so that the service profile for the SPID is allocated to the second terminal apparatus. If no user is present at the first terminal apparatus, it will be impossible for the user of the second terminal apparatus to use the service profile at the second terminal apparatus.
When a first service profile of a terminal apparatus is switched to a second service profile, information related to the second service profile is transmitted from the network to the terminal apparatus. Until the information is completely downloaded, the terminal apparatus is incapable of starting communication. According to the downloading information, functions are allocated to physical keys of the terminal apparatus. This function assignment is sometimes inconvenient for the user, and therefore, the user must reallocate the functions to the keys. Every time information is downloaded, this kind of confusion occurs.